Or are there technical reasons it can’t be scaled up to something the size of the shuttle?
In contrast the shuttle is returning from orbit while Spaceship One is not. The difference in speeds is considerable. The shuttles enters at Mach 20 or so while SS1 returns at around Mach 2-3. Perhaps a modified design could withstand the stress but I don’t know.
The article is misleading. SpaceShipOne doesn’t need elaborate heat shields because it’s a suborbital spacecraft and never comes close to orbital speed (~7km/s). The reentry speed of an orbital spacecraft is almost 10 times faster than that of SpaceShipOne. That’s 100x more kinetic energy that must be converted to heat (or some other form).
As I understand it, the folding wing transforms the spacecraft into a shape that drops through the atmosphere without tumbling or spinning. It’s more stable and foolproof than a controlled flight. The technology might be applicable to orbital spacecraft, but it doesn’t eliminate the need for heat shields.
Try calculating the difference in kinetic energy between the two vehicles. For the Shuttle during reentry, it’s about 3 trillion Joules. For SpaceShipOne during reentry, it’s about 2 billion Joules. Almost all of that energy must be dissipated before landing. A Hummer cruising down the highway at 70 mph is about 1.5 million Joules.
At the same time as it provides more aerodynamic braking than would a fixed inherently-stable geometry, that also had to work during both climb and landing-glide stages.
Also, I just had the thought that ideally, if you wanted to be extra-safe, you would want to build it so that if the variable-geometry mechanism were damaged, you could just hard-lock the wing into plain lifting configuration and do an old-fashioned long-glide banking reentry like the one the STS-class shuttles do.
Well, Burt Rutan appearantly thinks it can be done. When SS1 won the X-Prize, the Discovery Channel ran a show about the developement and flights. At one point Rutan was discussing follow up vehicles and showed on his computer pictures of both a larger sub-orbital vehicle (presumably the one being developed for Virgin Galactic) and an orbital version.
I’ve got several screen captures here.